JP2779028B2 - High titanium content aggregates sintered - Google Patents

Abstract

A process for increasing the particle size of fines of a titaniferous mineral containing more than 45 % by weight of titanium. The process comprises mixing the fines with a binding agent and water to produce an agglomerate. The agglomerate is then dried and sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is titanium-containing (t suitable for forming a TiCl ₄
itanium-bearing).

In the conventional method, a high titanium dioxide content (Ti
O ₂ 85% or more) substances, according to the specification for the content of the particle size and impurity elements of the material, a preferred source for preparing TiCl _4.

TiCl ₄ is a low boiling liquid, purified by distillation and chemical methods, which can be burned in oxygen to generate TiO ₂ pigment and chlorine gas, or reacted with magnesium or electrolyzed To form metallic titanium.

The raw material, i.e., a titanium-containing mineral having a size of 100 to 300 [mu] m, is fed to a fluidized bed reactor, where the temperature range 900
Subject to reductive chlorination at ~ 1000 ° C. Petroleum coke or a similar highly immobilized carbon material is added to the bed as both a fuel and a reducing agent. Oxygen may be added to the inlet to maintain the reaction temperature. The TiCl ₄ product flows out of the reactor in gaseous form along with the gaseous chloride of the impurity element and the finely divided solid particles entrained from the fluidized bed. This gas is condensed with the solids removed. Said
The TiCl ₄ product is purified by distillation and chemical methods.

In the chlorination step, most metallic impurities form volatile chlorides, leaving the reactor is included in the TiCl ₄ stream. However, alkali metals and alkaline earth metals form relatively less volatile chlorides that are liquid at the reaction temperature, thus forming agglomerates in the bed until a potential shutdown occurs. Tend to. Therefore, the operators of the process usually place strict limits on the content of these elements in the feed.

Impurities such as iron deplete the coke due to their reduction, and more importantly, waste the expensive chlorine reagents lost in the iron chloride waste, and are economical in the process. Causes serious drawbacks. Silicon and aluminum are also partially chlorinated in the above method, resulting in excessive chlorine consumption. Aluminum chloride is also a source of corrosion in the equipment used in this method.

As the mineral particles become increasingly chlorinated, their size decreases to the extent that they become entrained in the gas stream and exits the reactor as unavoidable and irrecoverable losses.
Conventionally, the associated loss is 5-10% of the total mineral input. When the diameter of the supplied particles is reduced to less than 150 μm, the loss rate due to entrainment is relatively higher than that of the normally shaped material. Such losses are unacceptable in both economics and operability.

In an attempt to overcome these problems, the known prior art methods, TiO ₂ - containing material, bituminous, and mixtures of water-soluble binder and coking by the aggregated complex of particles, A particulate TiO ₂ -containing material has been prepared for fluidized bed chlorination. However, this prior art method is not industrially satisfactory.
One reason is because the method of the chlorination is reductive chlorination, carbon in the feed material is TiO ₂ - not have to exist in a specific ratio with respect containing material, which is complex This is because it is not suitable for developing strength. In addition, the resulting agglomerates collapse before complete chlorination, as the carbon is attacked, and materials of fairly fine particle size are lost in the process, associated with the airflow.

Another method described in the prior art uses an aqueous emulsion of asphalt as a binder when forming pellets of particulate titanium-containing material by extrusion. The process of slow curing at 1000 ° C. removes water from the pellets and converts organics to carbon. As a result of this curing treatment, solidification of the binder occurs in the pores and around the particles, and a strong bond is formed. No chemical bond has occurred between the binder and the titanium-containing material. The extrudate must be broken down to a size in the range close to the desired product size before curing. Thus, the need to circulate the cured particulate to otherwise reduce the strength of the product pellet is eliminated. This carbon contributes to the reductive chlorination process during chlorination of the pellet. Therefore, this product has similar disadvantages as described in the prior art examples.

It is an object of the present invention to overcome one or more of the problems found in fluidized bed chlorination of particulate titanium-containing materials.

Therefore, the present invention is a method for increasing the particle size of fine powder of titanium iron (II) mineral containing 45% by weight or more of titanium, wherein the fine powder is mixed with a binder and water to form an aggregate. And drying the agglomerate and sintering the agglomerate.

The formed agglomerated particles are resistant to degradation forces associated with transport and handling. Further, the aggregated particles are
It is also resistant to the physical, chemical and thermal decomposition forces associated with chlorination methods, including fluidized bed reductive chlorination methods.

The agglomerated particles can be produced in a preferred range of sizes adapted to the kinetic requirements of the fluidized bed reductive chlorination process. This size range is, for example, 100-500 μm, more preferably about 150-250 μm. If the particles fall below this range, they are lost during the reaction due to entrainment in the gas stream. If the particles are above the range, they will float in the fluidized bed and an inert layer will form at the bottom of the reactor.

The titanium-containing particles can be any suitable titanium-containing mineral or mineral group. The titanium-containing mineral may be natural or synthetic. The titanium-containing mineral may be a detrital mineral. Titanium exists in the titanium-containing mineral in the form of titanium dioxide. The titanium dioxide content in the titanium-containing mineral can be about 85% by weight or more. A preferred source of titanium dioxide content is a deposit containing any of the minerals rutile, anatase, and leucoxin.

The titanium-containing mineral may follow an initial concentration treatment after extraction. The initial concentration treatment can increase the average content of titanium dioxide to, for example, about 90% or more by weight.

This is one type of titanium-containing mineral. Deposits of titanium-containing minerals from Horsham, Victoria, Australia, are further characterized by conventional micronization. Unusual refinement suggests that most of the entrainment losses result from later processing by reductive chlorination in a fluidized bed.

The titanium-containing mineral may be present in the aggregated particles in an appropriate amount. The titanium-containing mineral may be present at about 95-99.5% by weight, based on the total weight of the sintered agglomerate.

The amount of water added can vary depending on the size distribution of the original titanium-containing particles and the required size of the agglomerates. The amount of water varies between about 5 and 15% by weight, preferably about 8% by weight, based on the total amount of titanium-containing particles, binder and water.

The binder or binders for the titanium-containing particles may be of any suitable type. The binder for the titanium-containing particles must be such as to form agglomerates that are resistant to physical, chemical, and thermal decomposition forces during the drying and burning steps of the process. The binder may be organic or inorganic, and may be a binder that forms ceramic or glass. The binder is
A binder containing no carbon may be used. A kind of binder can also be used. Two or more binders may be used in combination to impart strength under different operating conditions of the drying and burning steps.

Binders containing calcium or sodium are not preferred. This is because the calcium or sodium component in the binder reacts in the reductive chlorination process to form toxic liquid residues. The binder may contain calcium or sodium, but the addition of these elements must not result in chlorination problems.

The binder for the titanium-containing mineral will be one that does not significantly contaminate the bound titanium-containing particles for subsequent processes, such as reductive chlorination.

The binder for the titanium-containing particles is as follows:
-15) may include: 1) colloidal silica 2) silica, water-soluble silicate, or silica / fluorite mixture 3) clay minerals (including bentonite, kaolinite, and montmorillonite) 4) boehmite 5) boehmite / Silica mixture 6) Geothite 7) Lignosulphonic acid 8) Sodium carbonate (saturated aqueous solution) 9) Sodium silicate 10) Group II element carbonate / clay mineral mixture 11) Sugar-like sugar 12) Aluminum salt / Organic amide mixture 13) Organic and inorganic solutions containing titanium 14) Polyvinyl acetate 15) Organic binder emulsified with water.

The amount of binder relative to the titanium-containing particles must be sufficient to produce effective agglomerates.
The amount of the binder should preferably not be high enough to enclose the titanium-containing particles. Preferably, the binder is relatively low. The range of this ratio is approximately
It is preferably from 0.5 to 5% by weight.

The mixing step in the method of the present invention can be done by any suitable method. Agglomeration is accomplished in a rotating disk- or drum-shaped pelletizer, or in a device incorporating rolling / tumbling motion, such as a V-blender, with a high strength micro-agglomerator.
ator) or a mixer, such as a mixer, or in a device that incorporates both of these operations. Agglomeration may be carried out in a process or in a closed circuit in combination with a screen for sizing the product.

The drying step may be performed by increasing the temperature from, for example, 75 ° C to 150 ° C. The drying step is preferably performed in such a way that the time that the agglomerates stay in this step during the process is limited to less than 30 minutes. The drying step may be performed by any suitable drying device. A fluid bed dryer or a rotary dryer may be used.

In the combustion step, the temperature and the residence time must be sufficient to form a homogeneous or heterogeneous phase that links the particles in the agglomerate. The agglomerate has a temperature of about 10
It can be heated to 00-1500C, preferably 1200-1400C. The time that the agglomerate stays within the temperature range may be about 5 minutes to 6 hours.

The combustion step may be performed by any of a number of suitable means, including combustion in a fluidized bed, oven, or kiln.

In a preferred form of the invention, the process may include a preliminary step of grinding at least a portion of the titanium-containing particle species.

The use of the pre-milling step can improve the size control in the preparation of the agglomerate and provide greater strength and density to the burned product. The titanium particles can be introduced into any suitable mill. Ball mills, rod mills, or heavy mills may be used.

The amount of titanium-containing raw material to be milled varies from 0 to about 100% by weight, depending on the type or type of titanium-containing material.

The milling step can provide particles having an average size of about 1 μm to about 50 μm.

The sintered agglomerates may include a large number of sintered agglomerated particles. The bond formed between the titanium-containing particles may include grain boundary recrystallization, ie, the boundaries of the titanium-containing particles are physically fused. The bonds formed between the titanium-containing particles may further include cross-linking by a second phase formed by the binder. The sintering step may tend to reduce or remove binder from the agglomerated particles. The initial binder may be largely or partially burned off. The initial binder may be present and / or incorporated into most or part of the crystal lattice in the particles.

The invention will be described in more detail with reference to the following examples.
However, the following description is merely illustrative of the invention and is not intended to limit the scope of the invention described above.

Example 1 First, using a laboratory scale batch-type Patterson-Kelly V-blender, 9.2 kg of dried leukoxin with 1% of dried bentonite powder.
Was blended for 1-2 minutes. The leucoxin was composed of 75% of the size range of 50-100 μm and 25% of the size range of 5050 μm. The size distribution of the two parts is recorded in Tables 1 and 2.

The V-blender was rotated at a speed of 40 rpm. Next, in a blender shell, the mixture was added to 1500
Water was introduced through an intensifier bar rotating at ~ 3000 rpm. The reinforcing bar exerted both a shearing action on the solids and an action of spraying water on the final divided form of the packing. The water added was about 8% of the fixed weight and the time required for this addition was about 4 minutes. In addition, a mixing time of 1-2 minutes allowed the microagglomerate to achieve final size and compaction.

Next, drain the product onto a large tray, spread it,
Oven drying at 80 ° C. for 48 hours to ensure complete drying. A 100 g sample of this microaggregate was placed on a ceramic dish and heated at 1260 ° C. for 25 minutes. The sintered product was then determined for its suitability as a feed for reductive chlorination according to a number of suitable physical and chemical tests.

Visual inspection of the micro-agglomerates after sintering revealed two distinct changes compared to the unsintered but dried material. First, shrinkage occurs either due to shrinkage in the internal voids of the micro-aggregates or shrinkage of the inter-particle voids of the agglomerates during sintering. Second, the color of the material has changed from grayish brown to reddish brown. Furthermore, the material exhibited a glassy or reflective state compared to the cloudy surface of the unfired material.

Examination of the sintered product with a microscope showed that the particles were densely packed in microaggregates with abundant crosslinks between the particles. Electron microscopy analysis showed that there was no structural difference between the material containing the crosslinks and the particles. No visible degradation or aggregate-aggregate adhesion was observed as a result of firing. Analysis of the calcined microaggregate by X-ray diffraction showed mainly a rutile phase and a pseudobrookite phase, a crystalline phase that could be formed only from the original leucoxin.

 Table 3 shows the size of the product after firing.

A "strength test" was performed on the microaggregate as follows; the microaggregate was placed between two glass slides and a load was applied until the microaggregate first broke. . The first failure is when the load is 1 kg (ie 10
When N) was exceeded, aggregates of 300 μm were generated. The broken pieces were of a uniform size, ie, had little or no tendency to dust. Calculations have shown that, due to this recorded strength, the agglomerates can be stored without breaking even at the pile and storage bottle compression forces of about 50 m height.

More quantitative and reproducible tests were performed to evaluate the resistance to friction. This test involves vigorously shaking 1 g of microaggregate fragments of approximately the same size (250-335 μm) in a cylindrical tube with an inner diameter of 18 mm, a length of 50 mm and three 8 mm diameter ceramic balls for 5 minutes. By doing that. During this test, the material is subject to both impact and attrition. The average particle size after the test is 303
μm to 170 μm. This is in contrast to a similar sample of original leucoxin, which was reduced to 220 μm.

It can be concluded that the micro-aggregates are industrially useful substances in terms of storage and transport.

For a small sample (10 g) of microaggregate, temperature 950 ~
Fluid bed chlorination tests were performed in a laboratory scale reactor at 1100 ° C. The results showed that when the chlorination was more than 50% complete: (1) there was no indication of a preferential attack on particle binding. Rather, this bond appeared to be relatively inert compared to the main mass of each mineral particle.

(2) At places where titania was partially removed in the microaggregate, unreacted core of the substance in its original state (apart from dye bleaching) remained inside the microaggregate. The size of the affected outer shell pores increased significantly.

Table 4 shows the size distribution of the burned agglomerates before chlorination in a laboratory fluidized bed test and after 89% chlorination. Obviously ~ 90μm
Shows that little chlorination is occurring and that a high degree of chlorination can be achieved if there is no bond breakdown or loss from the reactor such as fines carried in the exhaust gas. Have been. Similar results are obtained with up to 95% completion.

The fluidization performance of the microaggregate is evaluated as a function of its size and compared to the behavior of theoretical spheres, petroleum coke and gravel leukoxin. The results are plotted as the mean minimum fluidization rate in room temperature air versus the average particle size and are shown in FIG. These results indicate that the minimum fluidization rate expected at the smaller particle size is higher than the expected minimum fluidization rate at the larger particle size. This behavior can be explained in part by the influence of the size distribution and in part by the effects of concentration, surface shape and roughness. The chlorination process can be acceptable for agglomerates particles that are much larger than in the case of conventional feedstocks and makes it possible to improve the recovery of the process.

Example 2 Approximately 10 g of ground leucoxin was agglomerated and dried in the manner described in Example 1.

This fine agglomerate was fed to a small laboratory scale fluidized bed furnace and the bed temperature was maintained at 1260 ° C. The operating parameters of the furnace were as follows: bed diameter 30 cm wind box temperature 1000 ° C. wind box fuel LPG floor fuel coconut shell charcoal surface gas velocity 71 cm sec ^-1 agglomerate feed rate 22 kghr ^-1 said bed It has been found that enrichment with inert gas along with oxygen is necessary on this small device in order to control both temperature and surface gas flow rates within the desired range.

 The average residence time of the material inside the bed was about 20 minutes.

The amount of bed material lost due to entrainment in the exhaust gas was estimated to be 4.5%. Figure 2 shows the size distribution of feedstock, product, and carryover material.

The product was subjected to the rub-mill test described in Example 1. As a result, it was shown that the average particle size was reduced from 303 μm to 190 μm.

Example 3 An agglutination test was performed on a sample of rutile powder having the following size distribution: Agglomeration was performed using a "Flexomix" aggregator from Shugi Process Engineers (Lelystad, The Netherlands) at a solids feed rate of 840 kg / hr. Bentonite was added to the feedstock at 1% and premixed, and lignosulfonate was added per hour to a solids content of 2.
Added as 8 kg of 33% solution. In addition to the addition of lignosulfonate, water was introduced for 1 min. ^-1 .

After continuous passage through the agglomerator and fluidized bed, 67.5% of the dry units of the product had a size range of 125-500 μm. Products coarser than 125 μm in diameter were collected in a kiln for subsequent firing.

The agglomerates were fired in a rotary kiln that was burned with backflow oil 3.6 m long and 0.23 m inside diameter. Rotation speed 2rp
The residence time of the agglomerates in the high temperature region of 1260 ° C., at m. In this kiln, a total of 60 kg of aggregate was fired at a feed rate of 16.2 kg per hour.

Removal of the fines in the feedstock and the decomposed matter formed during combustion from the kiln by the combustion gas resulted in a feedstock yield of 69% of the product in the kiln. The size distribution of the feed and product particles is described below: Continuous agglomeration was attempted using an industrial blender manufactured by Patterson Kelley Pty. Ltd., Pennsylvania, USA. The milled leucoxin feed had the following size distribution: In the blender, per milled leucoxin hour
0.6 tonnes were fed in with an additional 6 kg per bentonite hour and 1.5 kg per organic binder (PVA) hour. Water, equivalent to 10% of the feed weight, was added by a spray mounted on the shaft of a set of high speed rotating blades in a coagulation chamber. The residence time of the mineral in this aggregator is
About 20 minutes.

The coagulated product is heated up to 80 ° C in a flat dryer.
Allowed to dry.

The particle size distribution of the dried product is shown below: The dried agglomerated product was fed to a 1250 ° C. fluidized bed calcining unit at 73 kg per hour. The fluidized bed firing unit had a diameter of 0.46 μm and a height (above the distribution plate) of 0.56 m. The flowing gas was the high air product of propane. The distillate was sprayed onto the bed of a fluidized bed and further heated by combustion with residual oxygen in the flowing gas. The residence time of the agglomerates in the fluidized bed was about 60 minutes.

Fines present in the feed and generated in the combustion fluidized bed were entrained in the exhaust combustion gases and removed through a thermal cyclone. Only 17% of the feed became "blowover" steam in this step.

The particle size distribution of the burned agglomerates and blowover of the fluidized bed is shown below:

Continued on the front page (72) Inventor Kalei, Ken George Australia, 3168, Victoria, Clayton, Bayview Avignon Commonwealth Scientific and Industrial Research Organization (72) Inventor Hollit, Mitchell John Australia, 3205, Victoria, South Melbourne, Bank Street 15, Second Floor, Wimmera Industrial Minerals Proprietary Limited (58) Areas surveyed (Int.Cl . ^6, DB name) C22B 1/16 C01G 23/02

Claims (19)

(57) [Claims] 1. A method for increasing the particle size of a finely divided titanium iron (II) mineral containing 45% by weight or more of titanium, wherein said finely divided mineral is mixed with a binder and water to form an aggregate. And drying the aggregate and sintering the aggregate. 2. The method of claim 1 wherein said binder is capable of forming a glass or exhibiting ceramic sintering properties when sintering said agglomerates. 3. The method according to claim 1, wherein said binder is selected from any compound selected from the group consisting of 1) to 15) below: 1) colloidal silica 2) silica, Water-soluble silicate or silica / fluorite mixture 3) clay minerals (including bentonite, kaolinite, and montmorillonite) 4) boehmite 5) boehmite / silica mixture 6) geothite 7) lignosulphonic acid 8) sodium carbonate (Saturated aqueous solution) 9) Sodium silicate 10) Group II element carbonate / clay mineral mixture 11) Sugar-like saccharides 12) Aluminum salt / organic amide mixture 13) Titanium-containing organic and inorganic solutions 14) Polyvinyl acetate 15) Organic binder emulsified with water. 4. The method according to claim 1, wherein said binder is bentonite. 5. The fine aggregate according to claim 1, wherein the aggregate is a fine aggregate formed by mixing a fine powder mineral, a binder, and water by applying a shearing action. Method. 6. The process according to claim 1, wherein the binder comprises, on a dry weight basis, 0.5 to 5% by weight of the total weight of the fines and the binder. 7. The method according to claim 1, wherein said binder comprises 5 to 15% by weight of the total weight of said fine powder, binder and water.
The method according to any of the above. 8. The method according to claim 1, wherein the aggregate is treated at a temperature of 75 to 150 ° C. for 30 minutes.
The method according to any one of claims 1 to 7, which is dried for less than a minute. 9. The method according to claim 1, wherein the agglomerate is sintered at a temperature in the range of 1000 to 1500 ° C. 10. The method according to claim 10, wherein the aggregate is heated in a temperature range of 1200 to 1400 ° C.
And sintering for 5 minutes to 6 hours. 11. The method according to claim 1, wherein the titanium iron (II) mineral is a finely divided mineral or a coarse-grained mineral. 12. The method of claim 11, wherein said mineral is ground to form a fine powder of said mineral. 13. The method of claim 12, wherein said mineral is ground to form particles having an average diameter in the range of 1 to 50 μm. 14. The sintered aggregate having an average particle size of 100
14. The method according to any of claims 1 to 13, wherein the method is in the range of -500 [mu] m. 15. The method according to claim 1, wherein the aggregate has an average particle size of 150 to 250 μm. 16. The method according to claim 1, wherein the mineral is a detrital mineral. 17. The method according to claim 1, wherein said mineral contains at least 85% by weight of titanium dioxide. 18. The method according to claim 1, wherein the mineral is rutile, anatase, or leucoxin. 19. An aggregate formed by the method according to any one of claims 1 to 18.